The separation and extraction of oil and bitumen from soil, sand, or other forms of mineral matter is a difficult and expensive process. For example, the commercial processes presently used to extract bitumen from Canadian oil sands involve crushing oil sand ore and combining it with hot or warm water and chemical aids such as sodium hydroxide (NaOH) to form a slurry. The chemical aids together with the mechanical action of transporting the slurry through a hydrotransport pipeline help to detach bitumen from the oil sand particles. The conditioned slurry is then discharged into separation cells and bitumen is separated from water by aeration to form a bitumen containing froth that can be skimmed off the surface of the water. Such commercial processes require a large amount of energy and result in the generation of significant quantities of tailings and waste process water. The need for large amounts of water is one of the reasons that U.S. reserves of tar sands (estimated to be 32 billion barrels of oil) have not been commercially developed. Energy and environmental concerns also bedevil the separation of oil or tar from the contaminated sand that is a result of conventional drilling operations (e.g., oil coated drill cuttings) or some of the newer technologies used to extract heavy oil, such as steam assisted gravity drainage (SAGD).
Because of the environmental concerns posed by warm water based extractions, work on solvent extraction of oil sands was studied. Solvent extraction methods, however, tend to produce bitumen with an excess amount of mineral fines, e.g., greater than 1%. Separated bitumen having an excess amount of mineral fines content require additional processing steps to reduce the mineral fines content to an acceptable level. In addition, solvent extraction methods require that residual solvent be recovered from the extracted sand.
The treatment and disposal of oil or bitumen contaminated sand and soil is a major problem after oil spills, either accidental, as in the Exxon Valdez or Deepwater Horizon incidents, or as a deliberate act of war, as in Kuwait. In addition, oily sludge (a mixture of heavy oil, mineral fines and water) is formed in storage tanks and supertankers and presents not only a major disposal problem, but also a significant loss of crude oil. It has been estimated that 1% 3% of the world's petroleum production is lost in the form of sludge and other wastes.
A number of treatment options can be applied to oil contaminated sand and rocks, including incineration, distillation, washing with detergents, extraction using organic solvents or bioremediation. Some of these methods have proved to be uneconomic because of their energy requirements, others do not completely remove the oil from the sand, or the chemicals used may pose unacceptable environmental concerns. None of these methods appear to be entirely satisfactory, but long-term storage (e.g., in landfills) of oil-contaminated sand is also a major problem.
The preferred solution would be to recover the oil for its economic value while generating sand in a clean form so that it can be used to repair environmental scars. This is not easy, because at least for waste materials the oil has usually weathered, lost much of its volatile component and is in the form of a viscous sludge or tar balls.
Hence there is a continuing need to develop technology that can economically separate hydrocarbons from inorganic solids including compositions of oil sands and hydrocarbon-solids compositions in good yields with minimal fines and with an improved impact on the environment.